In the long term evolution (LTE) system, the control signaling which needs to be transmitted in the uplink includes an acknowledgement/negative acknowledgement (ACK/NACK) message, and information reflecting the downlink physical channel state (CSI), which information has three forms: channel quality indication (CQI), pre-coding matrix indicator (PMI), and rank indicator (RI).
In the LTE, the feedback of channel information is mainly to use a feedback method with a relatively simple single codebook; however, the performance of the transmission pre-coding technology of MIMO more depends upon the feedback accuracy of the codebook.
Herein, the basic principle of channel information quantization feedback based on codebook will be described briefly as follows:
assuming that the limited feedback channel capacity is B bps/Hz, then the number of available codewords is N=2B. The characteristic vector space of the channel matrix constructs a codebook space ={F1, F2 . . . FN} after being quantized. The transmission end and receiving end together save or generate this codebook in real time (the transmission end and receiving end are the same). According to the channel matrix H obtained by the receiving end, the receiving end selects a codeword {circumflex over (F)} best matched the channel from  according to a certain rule and feeds back the codeword number i to the transmission end. Herein, the codeword number is referred to as PMI (pre-coding matrix indicator). The transmission end finds the corresponding pre-coding codeword {circumflex over (F)} according to this number i so as to obtain the channel information, and {circumflex over (F)} represents the characteristic vector information of the channel.
Generally,  can be further divided into codebooks corresponding to a plurality of Ranks, and each rank corresponds to a plurality of codewords so as to quantize the pre-coding matrix constructed by the channel characteristic vector under this rank. Since the rank of the channel is equal to the number of non-zero characteristic vectors, generally, when Rank is N, the codeword has N columns. Accordingly, the codebook  can be divided into a plurality of sub-codebooks according to different ranks, as shown in Table 1.
TABLE 1  Number of layers ν (Rank)12. . .N  1  2. . .  Ncodeword vectorcodeword matrixcodeword matrixcollection with thecollection with thecollection with thenumber of columnsnumber of columnsnumber of columnsbeing 1being 2being 2
In this case, when Rank >1, the codeword which needs to be stored is in the form of matrix, wherein the codebook in the LTE protocol exactly uses such feedback method of codebook quantization, and the downlink 4-transmission antenna codebook of the LTE is as shown in Table 2, actually, the meaning of the pre-coding codebook in the LTE and that of the channel information quantization codebook are the same. Hereinafter, for the sake of being uniform, the vector can also be regarded as a matrix of 1 dimension.
TABLE 2CodewordTotal number of layers ν (R1)Indexun12340u0 = [1 −1 −1 −1]TW0(1)W0(14)/{square root over (2)}W0(124)/{square root over (3)}W0(1234)/21u1 = [1 −j 1 j]TW1(1)W1(12)/{square root over (2)}W1(123)/{square root over (3)}W1(1234)/22u2 = [1 1 −1 1]TW2(1)W2(12)/{square root over (2)}W2(123)/{square root over (3)}W2(3214)/23u3 = [1 j 1 −j]TW3(1)W3(12)/{square root over (2)}W3(123)/{square root over (3)}W3(3214)/24u4 = [1 (−1 − j)/{square root over (2)} −j (1 − j)/{square root over (2)}]TW4(1)W4(14)/{square root over (2)}W4(124)/{square root over (3)}W4(1234)/25u5 = [1 (1 − j)/{square root over (2)} j (−1 − j)/{square root over (2)}]TW5(1)W5(14)/{square root over (2)}W5(124)/{square root over (3)}W5(1234)/26u6 = [1 (1 + j)/{square root over (2)} −j (−1 + j)/{square root over (2)}]TW6(1)W6(13)/{square root over (2)}W6(134)/{square root over (3)}W6(1324)/27u7 = [1 (−1 + j)/{square root over (2)} j (1 + j)/{square root over (2)}]TW7(1)W7(13)/{square root over (2)}W7(134)/{square root over (3)}W7(1324)/28u8 = [1 −1 1 1]TW8(1)W8(12)/{square root over (2)}W8(124)/{square root over (3)}W8(1234)/29u9 = [1 −j −1 −j]TW9(1)W9(14)/{square root over (2)}W9(134)/{square root over (3)}W9(1234)/210u10 = [1 1 1 −1]TW10(1)W10(13)/{square root over (2)}W10(123)/{square root over (3)}W10(1324)/211u11 = [1 j −1 j]TW11(1)W11(13)/{square root over (2)}W11(134)/{square root over (3)}W11(1324)/212u12 = [1 −1 −1 1]TW12(1)W12(12)/{square root over (2)}W12(123)/{square root over (3)}W12(1234)/213u13 = [1 −1 1 −1]TW13(1)W13(13)/{square root over (2)}W13(123)/{square root over (3)}W13(1324)/214u14 = [1 1 −1 −1]TW14(1)W14(13)/{square root over (2)}W14(123)/{square root over (3)}W14(3214)/215u15 = [1 1 1 1]TW15(1)W15(12)/{square root over (2)}W15(123)/{square root over (3)}W15(1234)/2
Where Wn=I−2ununH/unHun, I is a unit matrix, and Wk(j) represents the jth column vector of the matrix Wk. Wk(j1, j2, . . . jn) represents a matrix consisting of the (j1, j2, . . . , jn)th columns of the matrix Wk.
What is described above is the principle of the codebook feedback technology in the ITE, and when being applied, some more particular feedback methods will be related.
The feedback granularity of the channel information will be first introduced. In the LTE standard, the minimum feedback unit of the channel information is subband channel information, one subband is composed of several RBs (resource block), each RB is composed of a plurality of REs (resource element), RE is the minimum unit of the time frequency resource in the LTE, and the LTE-A continues to use the resource representation method in the LTE. A few subbands can be referred to as Multi-Subband, and several subbands can be referred to as Wideband.
Hereinafter, the feedback contents related to the channel information in the LTE will be introduced, and the channel state information feedback includes: channel quality indication (abbreviated as CQI), PMI and rank indicator (abbreviated as RI). Herein, the most concerned CSI content is PMI information, however, RI and CQI also belong to the feedback contents of the channel state information.
CQI is an indicator for measuring the quality of the downlink channel. In the 36-213 protocol, CQI is represented using integral values of 0-15, which represent different CQI levels respectively, and different CQIs correspond to their own modulation and coding scheme (MCS).
RI is used to describe the number of spatially independent channels and corresponds to the Rank of a channel response matrix. Under the open loop spatial multiplexing and closed loop spatial multiplexing, the UE needs to feed back the RI information, and the RI information need not be fed back under other modes. The rank of a channel matrix corresponds to the number of layers.
In the LTE system, the ACK/NACK acknowledge message is transmitted over the Physical Uplink Control Channel (PUCCH) in the format of 1/1a/1b (PUCCH format1/1a1/b), if the user equipment (UE) needs to send uplink data, then they are transmitted over the Physical Uplink Shared Channel (PUSCH), and the feedback of CQI/PMI and RI can be periodic feedback and can also be non-periodic feedback. Table 3 shows the uplink physical channels corresponding to periodic feedback and non-periodic feedback:
TABLE 3Periodic CQI reportNon-periodic CQI reportScheduling modechannelchannelFrequencyPUCCHnon-selectivityFrequencyPUCCHPUSCHselectivity
In this case, as to CQI/PMI and RI which are fed back periodically, if the UE does not need to send uplink data, then the CQI/PMI and RI which are fed back periodically are transmitted over the PUCCH in the format of 2/2a/2b (PUCCH format2/2a/2b), and if the UE needs to send uplink data, then the CQI/PMI and RI are transmitted over the PUSCH; and as to CQI/PMI and RI which are fed back non-periodically, they are only transmitted over PUSCH.
FIG. 1 shows a schematic diagram of an uplink control signaling being transmitted over the PUSCH in the LTE system, and the PUSCH carries uplink data and uplink control information, wherein the uplink control information includes CQI, PMI, RI and ACK/NACK.
FIG. 2 shows a schematic diagram of a PUSCH transmission mode in the LTE system, and it can be seen from the figure that the uplink data generates an SC-FDMA signal after being scrambled, modulated, transmitted and pre-coded, then RE mapped. PUSCH is transmitted in the form of single antenna, therefore, PUSCH only corresponds to one transmission block, which transmission block forms a codeword stream after being channel coded, that is to say, in the LTE system, the PUSCH only has one codeword stream.
In the LTE system, the eNB sends the modulation coding index IMCS to the UE via the PDCCH, which formulates relevant information such as the modulation coding index IMCS and the modulation of PUSCH, the size of the transmission block, the redundant version, etc., and the relationships therebetween, as shown in Table 4. In the LTE system, it is also formulated that the code rate is obtained according to the relationship between the size index of the transmission block and the size of the transmission block and according to the size of the transmission block and the size of the resource block.
TABLE 4ModulationModulationTransmissionRedundantcodingorderblockversionindex IMCSQm′size index ITBSrvidx020012102220323042405250626072708280929010210011410012411013412014413015414016415017416018417019418020419021619022620023621024622025623026624027625028626029Reserved1302313
The long term evolution advanced (LTE-A) system as the evolution standard of the LTE supports larger uplink transmission rate, therefore, the transmission of the PUSCH supports the form of spatial multiplexing. As to the PUSCH which is transmitted in the form of spatial multiplexing, the relevant art gives that the mapping relationship from the codeword stream to the layer is the same as the mapping from the codeword stream to the layer during the downlink transmission in the LTE system, and the particular mapping process is as shown in Table 5:
TABLE 5NumberNumberofofMapping from codeword to layerlayerscodewordsi = 0, 1, . . ., Msymblayer − 111x(0)(i) = d(0)(i)Msymblayer =Msymb(0)22x(0)(i) = d(0)(i)Msymblayer =x(1)(i) = d(1)(i)Msymb(0) = Msymb(1)21x(0)(i) = d(0)(2i)Msymblayer =x(1)(i) = d(0)(2i + 1)Msymb(0)/232x(0)(i) = d(0)(i)Msymblayer = Msymb(0) =x(1)(i) = d(1)(2i)Msymb(1)/2x(2)(i) = d(1)(2i + 1)42x(0)(i) = d(0)(2i)Msymblayer = Msymb(0)/2 =x(2)(i) = d(1)(2i)Msymb(1)/2x(1)(i) = d(0) (2i + 1)x(3)(i) = d(1)(2i + 1)
Where, Msymblayer represents the data amount transmitted over each layer, Msymb(0) and Msymblayer respectively represent the symbol number on each codeword stream, d(0)(i), d(1)(i), and d(l)(i) respectively represent the data over each codeword stream, and x(0)(i), . . . , x(3)(i) respectively represent the data transmitted over each layer.
Currently, the relevant art sufficiently takes how to transmit the combined coding index of RI and PMI-1, the combined coding index of RI and PTI, PMI-1 and PMI-2 over the PUCCH in the LTE-A system into account. However, the relevant art fails to take the following into account: how to transmit a periodic feedback report over the PUSCH, such as the combined coding index of RI and PMI-1, the combined coding index of RI and PTI, PMI-1, PMI-2, etc., which causes that the periodic feedback report cannot be transmitted over the PUCCH in the LTE-A system.